There are many arrangements in the prior art having the objective of redirecting the flow of exhaust from pneumatic tools to modify an operational characteristic thereof, such as noise. For example, U.S. Pat. No. 3,719,251, issued Mar. 6, 1973, relates to a diffuser apparatus for employment with a portable pneumatic tool such as a dentist drill to disperse exhausted air. The diffuser apparatus is formed as an integral unit of rigid material, such as metal or plastic, and incorporates an exhaust passageway formed into a plurality of spaced apart longitudinal passages. Each of the longitudinal passages are for communication with a plurality of spaced apart, annular transverse openings. The transverse openings, which are fixed in size and cannot be varied, connect the ambient atmosphere to the exhaust passageway.
U.S. Pat. No. 3,255,844, issued Jun. 14, 1966, discloses a multi-passage silencer for a pneumatic tool which consists of an assembly of thin rectangular plates stacked in uniformly spaced, fixed relation to each other. The air passing through the passageways defined by the plates to the ambient atmosphere allegedly reduces the noise of the exhaust gas.
U.S. Pat. No. 3,379,278, issued Apr. 23, 1968, discloses a muffler for use on a pneumatic tool such as a grinder. An open-ended sleeve of elastic, resilient material is tightly fitted over the body portion and exhaust ports of the tool, being bonded to the body portion. Spent air exhausted from the tool forces the sleeve away from the tool and escapes at the end of the sleeve.
U.S. Pat. No. 3,993,159, issued Nov. 23, 1976, discloses a muffler for reducing the noise level of the air exhaust from a governed pneumatic tool. The muffler, which is formed of plastic or metal, is secured to the tool housing by screws and forms an enclosed cavity extending about the exhaust apertures of the tool. A foraminous baffle plate, preferably a thin brass screen, is located within a cup-shaped body of the muffler.
U.S. Pat. No. 4,496,023, issued Jan. 29, 1985, discloses a plastic silencer surrounding a compressed air tool in the form of a pneumatically operated impact tool. The silencer forms an exhaust chamber around the tool. Two exhaust tubes project from the chamber and holes are drilled near the inlet ends of the tubes to prevent ice build-up.
U.S. Pat. No. 1,115,704, issued Nov. 3, 1914, discloses a pneumatic hammer muffler employing a leather sleeve or casing disposed about the tool. The casing is packed with a suitable fabric or waste to muffle the air as it exhausts.
My U.S. patent application Ser. No. 07/708,247, filed May 31, 1991, now U.S. Pat. No. 5,189,267, issued Feb. 23, 1993, relates to a muffler system for a pneumatic tool employing heat shrink tubing shrunk into position on the tool. Foraminous material is located between the tubing and tool in a restricted fluid-flow passageway extending between the tool air flow outlet and an end of the heat shrunk tubing.